Friday, July 1, 2011

Cisco IOS configuration examples

While getting ready for my CCNP exams, I purchased quite a few Cisco devices from our national eBay-clone site. While some folks don't really understand, why I don't just use GNS3 and be happy with it, I prefer the hands-on stuff very much. Here's why:

Things don't go wrong in the simulated stuff as often as they should, to help you learn;

I have a hardware technician past, so I just like the boxes;

You don't have to learn memory constraints and upgrades on a simulated router: you just set it to max RAM, best-newest image, boot, done. Real world is not this nice;

You don't have to recover from a failed IOS upgrade, or do a password recovery;

And your configs are just too clear.

The last part is one of my problems with official CCNP study materials too: they only config what the chapter wants you to learn. If, for example, you study EIGRP, there won't be serious security configured on the box.

Now this is the part where the second-hand Cisco gear comes in: if you buy it from non-IT people, who didn't use it in their own home lab, chances are, the original config will be there. And that's the way I managed to acquire some live configs from ISPs and corporations. It's not guaranteed that these configs are perfect, but they were running in production networks, every day. So I think they are worth checking out.

Now, before we begin, the usual disclaimer: I deleted sensitive data from the configs, like usernames and passwords, and phone numbers, but not IP addresses (except for AAA servers). Most of these IP addresses are still in use by these organizations, so please be a grow-up, and don't try to hack them. They have some smart guys to track you down, and you don't really want that.